Photographic reversal process



Patented June 12,1934

. rnorrooimrmo nEvEasAIi ra'oonss Edwin Ernest Jelley, Weald stone,England, assigner toEastman Kodak Company, Rochester;

N. Y., a corporation of New York l This invention relates to theproduction of positivephotographic images upon the same support inthesame sensitive layer as that which is exposed" in the camera by areversalprocess of the kind i-n which no exposure to actinic light ismade after the first development. In such processessodium sulphide or acompound of formaldehydeand sodium hydrosulphite has hitherto been usedto "fog or darken the image after the plate or filmhas" been treated inthe reversal bath but with the substances hitherto used it has not beenpossible'fsubsequently to employ the'usual photographic developers andas a result'the'control image has been considerably restricted.

'Ihe object'of the present invention is to providea process by whichthese disadvantages can be overcome.

. l 'Accordin g t'o-this invention the him after it has been submittedt" the reversal bath is treated with ance or a selected dye-stufi, initself well known,

' prior to redevelopment with any suitable known "photographic developeror in conjunction with As a result the colour and opacitysuch'develope'r. of the final image can be controlledwithinwide limitsduring'the'final developing operation even the case "of v ry thinemulsions.

-. m' b tances found suitable for use as nucleus forming or ioggingagents prior-to or in con"unction with (well-known photographicdevelopers, are sodium hydrosulphite, methylene blue, hydrazine and;hydrogen peroxide.

Theuse of'hydraz'ine tends to cause the'ernul sion' to separate from itssupport during the redevelopment of the film owing to the gas which isthen evolved and to counteract this it is therefore necessary for thedeveloper to contain an aldehyde or ketone such for example asformaldehyde acetone or acetaldehyde which combines chemically with theexcess of hydrazine and yields an inert compound.

The following are specific examples of 'how the invention can be carriedout.

Example I .-The sensitive plate, film or paper (hereafter referred to asa film) is first exposed in the usual way in the photographic apparatusand fully developed in any known suitable developer such for example asone made up of equal parts of the following solutions:---

Solution A Ounces Hydroquinone 2 sodium bisulphite 3 Formalin(Commercial) 2 Water to make fluid ounces of the op'acityand colour ofthe final positive "a nucleus forming agent such as a reducing subin acaustic hydroquinone developer as above deafter bein'g treated in a 10%aqueous solution of N0 Drawing. Application April, 2, 19 30,[Serial InGreat Britain November 13,

Waterto make 80 fluid ounces Afterbeing washed for about a minute thefilm is bleached in a solution which may be as follows:-.-

1 Potassium bichromate. ounce- Sulphuric acid -4 1 fiuid ounces Watertomake80 fluid ounces 70 The filmis then again washedand immersed in aclearing hath made up as follows:--

. 7 Parts Sodium sulphite 10 Sodium hydro'sulphite 2 Water L' 87 /2After being rinsed, the mm is then developed scribed and subsequentlygiven such washing or other treatment as would be necessaryor'customary,and is dried in the usual manner.

Example II. The film is exposed, developed and bleached'inthe mannerabove described and 85 sodium sulphite is immersed in a separate bathcontaining an aqueous solution of 0.01% methylene blue prior to beingredeveloped and treated in the'm'anner already described.

' Example 1II.-'-Instead'of the'film being submittedto the action ofa'fogging or nucleusforming agent prior to redevelopment, this agent isincorporated in the redeveloping bath. The film after beingdevelopedandclea'red' in a 20% aqueous solution of sodium sulphite is washed andimmersed in a caustic hydroquinone developing bath (made up as alreadydescribed) containing in addition one part of methylene blue to every1000 parts of developing solution. The addition of this dye-stuff to thedeveloping bath enables the opacity and colour of the image to becontrolled within wide limits and eliminates the separate step oftreating the film in a bath containing afogging or nucleus-forming agentprior to redevelopment.

It will be appreciated that the particular solutions stated above aregiven by way of example; only and that considerable modifications may bemade in the process within the limits of the invention.

What I claim as my invention and desire to secure by Letters Patentis:--

1. In a process of making positive photographic images by reversal fromnegative photographic images in a light-sensitive element which processcomprises rendering the negative image inert and transparent, treatingthe light-sensitive element by chemical means to render it developableand then developing the sensitive element, the improved step ofsubmitting said element, before development begins, to the action of asolution containing methylene blue as a nucleus-forming agent for thesensitive element.

2. In a process of making positive photographic images by reversal fromnegative photographic images in a light-sensitive element which processcomprises rendering the negative image inert and transparent, treatingthe light-sensitive element by chemical means to render it developableand then developing the sensitive element, the improved step ofsubmitting said element, before development begins, to the action of asolution containing hydrazine as a nucleus-forming agent Ior 4 thesensitive element.

3. A process of making positive photographic images by reversal fromnegative photographic images in a light-sensitive element whichcomprises bleaching in an aqueous solution of potassium bichromate andsulphuric acid, treating the light-sensitive element with an aqueoussolution of sodium sulphite and sodium hydrosul phite and developing thesensitive element in a caustic hydroquinone developer.

4. A process of making positive photographic images by reversal fromnegative photographic images in a light-sensitive element whichcomprises bleaching in an aqueous solution of potassium bichromate andsulphuric acid, clearing and treating the light-sensitive element byimmersion respectively in a 10% aqueous solution of sodium sulphite andthen in an aqueous solution of 0.01% methylene blue and developing thesensitive element in a caustic hydroquinone developer.

5. A process of making positive photographic images by reversal fromnegative photographic images in a light-sensitive element whichcomprises bleaching in an aqueous solution of potassium bichromate andsulphuric acid, immersing the light-sensitive element in an aqueousclearing solution of 20% sodium sulphite and developing in a solution ofa caustic hydroquinone developer containing one part of methylene blueto every 1000 parts of developing solution.

6. In a process of making positive photographic images by reversal fromnegative photographic images in a light-sensitive element which processcomprises rendering the negative image inert and transparent, treatingthe light-sensitive ele- .ment by chemical means to render itdevelopable and then developing the sensitive element, the

improved step of submitting said element, before development begins, tothe action of a solution containing hydrazine as a nucleus-forming agentfor the sensitive element and adding an aldehyde to the solution used inthe subsequent developing.

7. In a process of making positive photographic images by reversal fromnegative photographic images in a light-sensitive element which processcomprises rendering the negative image inert and transparent, treatingthe light-sensitive element by chemical means to render it developableand then developing the sensitive element, the improved step ofsubmitting said element, before development begins, to the action of asolution containing hydrazine as a nucleus-forming agent for thesensitive element and adding a ketone to the solution used in thesubsequent developing.

. 8. In a process for making positive photographic images by reversalfrom negative photographic images in a light-sensitive element, whichprocess comprises rendering the negative image inert and transparent andthen redeveloping the sensitive element, the improved step of renderingthe element redevelopable, without reexposure, in developers havingordinary developing properties that comprises submitting the element toa bath including hydrazine.

9. In a process for making positive photographic images by reversal fromnegative photographic images in a light-sensitive element, which processcomprises rendering the negative image inert and transparent and thenredeveloping the sensitive element, the improved step of rendering theelement redevelopable without reexposure, in developers having ordinarydeveloping properties that comprises submitting the element to a bathincluding methylene blue.

10. A photographic reversal process comprising the formation of a silverimage in a light sensitive, silver halide, emulsion layer, rendering thesilver image inert and transparent, treating the remaining silver saltswith a bath including a nucleus forming agent and redeveloping the saltswith an agent other than the nucleus forming agent.

11. A photographic reversal process comprising the formation of a silverimage in a light sensitive, silver halide, emulsion layer, rendering thesilver image inert and transparent, treating the remaining silver saltswithsodium hydrosulfite to an extent insuflicient to reduce theremaining silver salts but suflicient to render them developable, andredeveloping the salts with an agent other than the sodium hydrosulflte.

EDWIN ERNEST J ELLEY.

